1. Field of the Invention
The present invention relates to a television broadcast signal receiving apparatus capable of receiving television broadcast signals of the UHF band and the VHF band, and more particularly to a television broadcast signal receiving apparatus having a channel auto scan (channel auto setting) function using a multidirectional antenna.
2. Description of Related Art
Because plain areas are dotted with large cities and are provided with many broadcasting stations in the North American Continent where the ATSC digital television broadcast (hereinafter abbreviated as TV broadcast) is performed, TV broadcast signals are transmitted from various directions. In such an environment, a viewer receiving the TV broadcast signals is required to adjust the reception direction of an antenna into the direction of the broadcasting station broadcasting the program that the viewer wants to watch. Accordingly, a multidirectional antenna such as a smart antenna has been put to practical use.
Moreover, the EIA-909 standard defines the smart antenna to have a reception direction in each direction obtained by dividing a circle into 16 directions. On the other hand, a digital TV broadcast signal receiving apparatus in conformity with the EIA-909 standard is configured to be capable of controlling reception directions into all of the 16 directions receivable with the smart antenna.
On the other hand, in order to receive a broadcast signal from each broadcasting station in a television broadcast signal receiving apparatus, it is necessary to execute the processing called channel auto scan (channel preset). It is desirable for a viewer to complete the channel auto scan processing in a time as short as possible.
For example, as the technologies concerning the channel auto scan or the channel preset, the inventions described in Japanese Utility Model Registration No. 3070655, Japanese Patent Application Publication Laid-open No. 08-097683 (Japanese Patent No. 3166810), Japanese Patent Application Publication Laid-open No. 2003-273759, Japanese Patent Application Publication Laid-open No. 2005-159810 and Japanese Patent Application Publication Laid-open No. 2005-045592 were proposed.
Now, the digitalization of terrestrial broadcasting has rapidly advanced in recent years in each country of the world. Although the digital terrestrial broadcasting is broadcasted in parallel to the existing UHF analog broadcasts, each of the assigned channel frequencies can simultaneously transmit five to six programs. The digital terrestrial broadcasting consequently has an advantage capable of settling a frequency tightness problem by using vacant frequencies in various fields. Moreover, it is determined that the analog terrestrial broadcasting will be abolished and completely veer to digital terrestrial broadcasting in several years, and the broadcasts using the VHF band will be reduced to be stopped in future together with the abolishment of the analog terrestrial broadcasting.
Under such a situation, because channels that are not received (vacant channels) becomes many, the use of the technologies disclosed in the above prior applications in the setting of a channel corresponding to a broadcast signal of the VHF band would cost a superfluously waste time. That is, if the presetting of a channel using the technologies of the above prior applications is executed, scanning is similarly performed to the TV broadcast signals even if the signals is of either of the VHF band and the UHF band. Consequently, it is conceivable that there is further room for improvement.